1. Field
An aspect of the described technology relates generally to a sputtering apparatus for depositing an extremely low concentration of a metal catalyst on amorphous silicon to crystallize the amorphous silicon. More particularly, an aspect of the described technology relates to a sputtering apparatus capable of sufficiently carrying out a pre-sputtering process in a short time and, thus, uniformly and stably depositing the extremely low concentration of the metal catalyst on the amorphous silicon without reducing efficiency of an overall deposition process.
2. Description of the Related Art
Flat panel display devices may replace cathode ray tube display devices due to their characteristics, e.g., a light weight, a thin thickness, and so on. Examples of the flat panel display devices may include liquid crystal displays (LCDs) and organic light emitting diode displays (OLEDs). For example, in comparison with the LCDs, the OLEDs exhibit excellent brightness and wide viewing angle characteristics and require no backlight, so that the OLEDs may be realized as ultra thin display devices.
The OLEDs may be classified into a passive matrix type and an active matrix type, according to a driving type. For example, the active matrix type-OLED may include a circuit using thin film transistors (TFTs).
The TFTs generally include a semiconductor layer having a source region, a drain region, and a channel region, and gate, source, and drain electrodes. The semiconductor layer may be formed of polycrystalline silicon (poly-Si) or amorphous silicon (a-Si). The poly-Si may exhibit higher electron mobility than the a-Si, so the poly-Si may be mainly applied at present.
The poly-Si semiconductor layer of the TFT may be formed by crystallizing the a-Si, e.g., by using a metal. A crystallization method using metal may crystallize the a-Si at a relatively low temperature in a short time by depositing a metal catalyst on a substrate. For example, a crystallization-inducing metal, e.g., nickel, may be deposited via sputtering on a substrate from a metal target made of the crystallization-inducing metal using plasma. In another example, the crystallization-inducing metal may be deposited via an atomic layer deposition (ALD) on the substrate using a chemical method based on a reaction gas containing the metal catalyst as the crystallization-inducing metal, so the a-Si may be crystallized using the metal catalyst as a seed.